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Some bettas can do fine with guppies actually. But not all. You'd have better luck with females. As for cories, I would say most are fine. Any I have tried ignored the cories. Depends on your fish.
Bettas and corys are fine together but you will need a filter if you're keeping corys. Corys have a habit of kicking up dust and debris so if there's no filter your water will become cloudy fast